Method of making sulphur-free water gas



c. s. PALMER.

METHOD OF MAKING SULPHUR FREE WATER GAS.

APPLICATION FILED JUNE 3,1918.

Patented Feb. 7, 1922.

ll/l Ill/[1111 lull/ll ll/I/I I Ill/IL] j/z 2 6/2221: M 124),

CHARLES S. PALMER, 0F PITTSBURGH, PENNSYEVANIA.

METHOD GE MAIKHG SULEH'UR-EREE WATER @5152.

mosse Specification of Letters E'atent.

Patented Feb. 7, @9 22.

Application filed June 3,1918. Serial No. 238,921}.

of Pennsylvania, have invented certain new and useful Improvements inMethods of Making Sulphur-Free Water Gas, of which the following is aspecification.

My invention relates to improvements in the manufacture of combustiblegases from wood or charcoal and has for its objects the economical andconvenient production of a substantially sulphur-free water-gas, themanufacture of charcoal and the Water-gas therefrom being preferablycarried out by successive operations in the same apparatus. althoughobviously if desired the successive steps of the manufacture may beconducted in difi'erent units of the plant.

The present process of manufacturing water-gas as at present commonlypracticed is highly wasteful, in tact about to more coal is consumed inthe process merely for maintaining the necessary heat for the water-gasreaction than is necessary, i. e. the present practice consumes about50% of hard coal or coke for maintaining the reaction temperature,whereas, theoretically but about should be required. A similar losswould occur if charcoal were used in lieu of coal or coke as the fueltreated. Primarily tiis is due to the wasteful employmentof anintermittent air blast for periodi cally restoring the temperature ofreaction as well as being due to the great length of time required whenemploying the modern retorts in order to heat the contents to thereacting temperature and the consequent serious loss of heat throughoutsaid period by radiation and otherwise.

My invention is fully set forth and de-d chamber or retort, preferablyfor example of about 205x. 10 and 8 to 10 wide having a ii-shapedbottom, the walls being about in thickness. The heating chambercommunicates with the usual checker-Work of regenerator furnacespositioned below the same (not shown). Preferably such retort isconstructed in sections and the same are constructed' of a highlyrefractory, nonnidizable metal such as ni-chrome steel, though' nickelsteel or nickel may be also employed in lieu thereof. Suitable pokeholes a and charging holes 1) are provided at the top of the retort asshown. The lower section pref erably has cast iron extensions 3, 3,-comoil municating with a suitable discharge reseryoir for any residuumat the end 3 and havmg. a sultable cast iron door 4: covering the end orextension 3. A gas outlet conduit 5 communicates With-the interior ofsaid retort through the said end 3. In the apex of the bottom of thelower section is a longitudinal steam line 6 whichhas perforations c atintervals along the top in order to uniformly admit steam into the.bottom or the retort.

Referring to the drawings and the construction shown therein, theoperation of the process is as follows Sufiicient hard Wood adapted toyield a good grade of sulphur-tree charcoal is introduced through thecharging holes to substantially till the entire retort. Such. Wood isthen subjected to destructive distillation to obtain the volatileproducts, pyroligneous acid etc. therefrom by means of heat conductedthereto through the highly conductive, thin, metallic walls of the pipe5, to containers or reservoirs therefor and the charcoal residuum may beremoved into another similar retort through the outlet 3. in order tosubject the same to the second stage of the process, but preferably saidsecond stage is conducted in the same retort. The volatile products ofdestructive distillation so obtained may be suitably scrubbed andotherwise treated in the well known manner to obtain the usualby-products therefrom.

Owing to the high conductivity of the thin walls of my retort, which arepreferably about 3; thick, and should not exceed 1%" in thickness inevent, even the first stage may be accomplished in a shorter space oftime than the process commonly employed at present and as consequencethere is but a minimum of fuel and time required for this stage of theprocess.

In order to produce water-gas from the charcoal residuum of the firststage of the process, the retort is first sufficiently heated y theregenerator furnace gases passing through the tines so as to maintainthe mass incandescent by indirect heat only, throughout the second stageof the process, preferably at about 110.) C. Steam is then introducedthrough the steam-line 6 in sutlicient quantities to convert theincandescent coke into water-gas according to the formula C+H ():H +CO.Preferably the steam is superheated, superheating being decided moreefiicient. Owing to the above stated high heat conductivity of the thinmetal walls of my retort, this second stage of the process is completedvery rapidly as compared with the usual procedure and the periodicallyinjected hot blasts of atmospheric air are not required in order tomaintain the requisite temperatures for the production of water-gas.

Ni-chrome, and other nickelous alloys consisting principally of nickel,and even nickel itself, unlike iron, ordinarily, while diflicultlyoxidizable at high temperatures, soon becomes superficially loaded withcarbon, when subjected to direct contact with very hot reducing gaseshaving a high carbon content, particularly at temperatures between 1000and 1100 C. Not only is such carbon physically deposited upon andthroughout the exposed surface layer of the metal as graphitic carbon,but also it will be found to be in chemical combination therewith in theform of carbides. The consequence of such loading of nickelous metalwith caroon is that it rapidly deteriorates structurally, often becomesweakened to such an extent as to in many cases even crumble to pieceswhile being subjected to temperatures up to 1100 C., and furthermore itsspecific heat conductivity becomes very greatlyreduced. Under theconditions however to which the nickelous envelope is subjected duringthe operation of my process, theinner portion thereof is protected fromthe carbonizing or carbide-forming action of the reducing gases in theretort, because of the fact, as my investigations have shown, that thenickelous portion of the envelope is extremely thin and at-the hightemperature to which it is subjected, is at least partially pervious tothe passage thereinto of the strongly oxidizing external gaseous heatingmedium, such as the producergas and hot air mixture which is preferablyemployed by me. The result is that the deleterious action of thecarbonizing and carbide-forming gas within the retort upon the innerexposed layer of the envelope is substantially if not entirely,prevented, and instead of the structure of the envelope being seriouslyweakened and the specific heat conductivity of the envelope beinggreatly diminished, as would ordinarily be expected by those familiarwith the behavior of nickel and its alloys consisting essentially ofnickel, the envelope is found to be extraordinarily durable and evenafter repeated operations of my process herein to retain to a remarkable degree its specific conductivity.

In view of the high conductivity of the walls of the retort and theelimination of the necessity of injecting a blast of heated airthereinto as aforesaid, I am able to obtain from the charcoal a maximumyield of substantially sulphur-free water-gas mixture having a minimumamount of CO and substantially free from nitrogen, i. e., about 5% andless than 1% in all cases where the process is properly carried out.

The aforesaid ni-chrome alloy approximates in capacity Ni 50 to Cr 10 a)20% Fe 15 to 25% side to the inside of the retort is accomplished',whereas, were the walls constructed relatively thick, say in excess of14;, even though they were of metal, such transfer of the necessary heatto accomplish the quick conversion of the charcoal into water-gas couldnot be accomplished, and prolonged heating of the coke by the periodicin ection thereinto of hot blasts of air would be necessary in order toprevent the temperature falling below the point at which the water-gasreaction proceeds efliciently, because the reaction (3+2H2O:CO2+2H2which occurs at lower temperatures, must be avoided in order to obtainan eflicient and satisfactory substitute for natural gas.

In my preferred process I also employ nichrome steel or othercorrespondingly highly resistant non-oxidizable metal in the steam lineand the superheater, since not only am I thus able to superheat thesteam to the reaction temperature when desired, without {the destructionof the superheater, but also Iavoid the inevitable reduction intemperature which occurs upon the introduction of ordinary superheatedsteam, which usually is at temperature considen ably in excess ofordinary superheated steam. For example. a steam temperature of 750 to1100 is believed to materially I promote the dissociation the steam,thereby increasing the chemical activity of its elements with theconsequence that formation of hydrocarbons by the interaction ofhydrogen of the and the carbon (charcoal) is accordingly facilitated.Such a superheater illustated in Fig. l i which a coil '4' is positionedin a superheatchamber 8, the said chamber being proded with gas inletand outlets 9 and 10 respectively. ln this construction the coil 7 andthe ire steam pipe 0 are formed of nirhro'me steel, nickel-steel, nickelor other suitable highlyrefractory, substantially non-oxidizable metalalloy consisting essentially-0t nickel or cobalt.

llhile nickel itself, when employed for the retort or the superheaterpiping, forms a thin superficial coating of nickel oxid, l have foundthat the formation of this crust does not seriously retard theconduction of heat therethrough and furthermore, that said crust doesnot increase thickness and *ause the deterioration or destruction of theretorts or superheater piping.-

As is apparent from the foregoing description, the employment or ahighly resistant. non-oxidizable metal retort, having walls notexceeding inches in thickness, has the following important advantagesover a great many of the present Water-gas processes as commerciallypracticed.

First, it avoids the necessity for quenching the charcoal alter theremoval of the charcoal from the still and prior to its in troductioninto the Water-gas retort, and thereby substantially all of the heatretained in the charcoal at the end of the first stage is conserved,since in my process, as above stated, the Water-gas process ispreferably conducted in the same retort as the distillation process andimmediately following the completion oi the latter.

Second. it avoids the necessity for the use of an intermittent air blastto maintain the reactingtemperature and thereby prevents the dilution ofthe gas with large amounts of nitrogen from the heated air blast, andalso the maintenance of the uniform temperature enables me to obtain amuch more economical and increased yield. of gas of a more uniformcomposition.

Third. the employment of nou-oxidizable highly-resistant metallic Walls,which should not exceed 1.; inches in thickness, and are preferably inchthick, as a substitute for cast iron or other oxidizable metal retortsor clay and silica retorts now used. permits or the reaction beingcompleted in a much shorter period of time because of the Water-gasreaction being continuous in but a. fraction of tllfi time required whenthe present retorts, which heat extremely slowly, are employed.

Fourth, one of the advantages of employing higlrp essure superheatedsteam at a temperature of 750 C1, to ll00 (1., is b lieved to be due tothe formation of increased amounts of higher hydrocarbon due to theincreased dissociation of the steam, since it is well known the theaddition of one or more atoms of carbon or hydrocarbon to a hydrocarbonin many cases Very substantially increases the thermal value thereoi.This is shown by the following table in which are given the relativethermal units per cubic foot of ditlerent hydrocarbons Cal. per kg.

tently, produce 500 to 1000 cubic feet of A water-gas per square foot ofheating surface in every hours, the same approximating the followingaverage composition Qt 27;, to 10% C l l heavy hydrocarbons 0.1% to 0.5%H, 50% to 60% Cd-l Paratlines 1% to 10% to 20% to 30% N Less than 1%Obviously in those cases Where the extension 3 is not in communicationwith the discharge reservoir for the coke residuum resulting from thesecond or water-gas stage of the process, said extension or end 3 isclosed in the same manner as extension 3 by a cast iron door (notshown.)

The employment of platinum, gold, iron (and by iron ll include the ironhaving such carbon content as to come Within the range commonly termedsteel). as the material of the envelope referred to in the processclaimed herein. or, as the material of the retort referred to in theapparatus claimed herein, is specifically disclaimed.

The expression a metal associated with iron in the iron group inMendeleefs table and of greater atomic Weight than iron. referred tometals which are associated with iron in the group commonly known as theiron group consisting of iron, atomic weight 55.84:, nickel, atomicweight 58.65 and cobalt, atomic weight 58.97

Having thus described my invention, what I claim and desire to secure byLetters Patent is 1. In the manufacture of water-gas from charcoal theprocess which consists in confining a charge of charcoal substantiallyfree from sulphur and its compounds, in a space having an envelope whichconsists principally of a metal associated with iron in the iron groupof Mendeleefs table and of greater atomic weight than iron, said onvelope not exceeding 1:}- inches inthickness, being of good heatconductivity and not deleteriously afiected when subjected to the actionof a mixture of producer gas and air heated to a temperature of 1100 (l,for prolonged periods of time, supplying sutlicient heat to said chargethrough said conductive envelope from a strongly oxidizing,highly-heated gaseous medium caused to contact with the outer surface ofsaid envelope, to promote the water-gas reaction in said charge,maintaining said temperature by conduction of heat to said chargethrough said conductive envelope without the direct introduction to saidchamber of substantial quantities of an air blast, simultaneouslysupplying a sufiicient quantity of steam to said charge to effect thewater-gas reaction so as to produce a strongly, reducing, highlyheated,gaseous medium in contact with a substantial portion of the innersurface of said envelope.

2. In the manufacture of water-gas from charcoal, the process whichconsists in con fining a charge of wood-charcoal in a space havin anenvelope which consists principally of a metal associated with iron inthe iron group in Mendeleefstable and of greater atomic weight thaniron, said envelope not exceeding 11?; inches in thickness, being ofgood heat conductivity and not deleteriously aiiected when subjected tothe action of a mixture of producer gas and air heated to a temperatureof 1100 (1., ior prolonged periods of time, supplying sufficient heat tosaid charge through said conductive envelope from a strongly, oxidizing,highlyheated gaseous medium ,caused to contact with the outer surface ofsaid envelope, to promote the water-gas reaction in said charge,maintaining said temperature by conduction of heat to said chargethrough said conductive envelope without the direct introduction to saidchamber of substantial quantities of an air blast, simultaneouslysupplying a sufficient quantity of highly supen heated steam at atemperature in excess of 750 C. to said charge, to effect the water-gasreaction, so as to produce a strongly, reducing, highly-heated, gaseousmedium in conmosses .velope not exceeding 1-} inches in thickness,

being of good heat conductivity and not deleteriously affected whensubjected to the action of a mixture of producer gas and air heated to atemperature of 1100 G, heating said charge by means of heat conductivitythrough said conductive envelope to a temperature sufiicient to dist-illthe volatile products from said charge and maintaining said temperatureuntil substantially all of the volatile matter is expelled, withdrawingthe liberated volatile substances from said chamber, then conductingsuthcient heat through the envelope of said space from a stronglyoxidizing, highly-heated, gaseous medium caused to contact with theouter surface of said envelope to elevate the temperature of theresidual charcoal therein so as to promote the water-gas reaction,maintaining the said reacting temperature of said coke, whilesimultaneously introducing steam, without the substantial introductionof oxygen, for a sufiicient time to convert the greater part of saidcoke into water-gas, and thereby produce a strongly reducinghighly-heated gaseous medium in contact with a substantial port-ion ofthe inner surface of said envelope and recovering the evolved water-gas.

4. In the manufacture of water-gas from charcoal, the process whichconsists in confining a charge of wood-charcoal substantially free fromsulphur and its compounds in a space having an envelope which includes amedium consisting principally of nickel, said envelope being of ood heatconductivity and being sufficiently thin to be substantially penetratedinto by an external strongly, oxidizing, highlyheated gaseous mediumbrought into contact with the outer surface of said envelope and alsosufliciently thin to permit of the substantial neutralizing of saidoxidizing medium of the graphite and carbide-forming tendency of astrongly reducing, highly-heated gaseous medium simultaneously broughtinto contact with the inner surface of saidenvelope, said envelope beingsubstantially non-oxidizable when subjected to the action of a mixtureof producer gas and air heated to a temperature of 1100 (l, supplyingsufficient heat to said charge through said conductive envelope, from astrongly oxidizing highly-heated gaseous medium caused to contact withthe outer surface of said en- Nil velope, topromote the Water-gasreactionin said charge, maintaining said temperature by continuedcenduction of heart from said; gaseous medium through said conduc- 5tive envelope to said charge Without the direet intreduction into saidchamber of substantial quantities of air, simultaneously supplying asuflicient quantity of steam to said charge to effect thewate'r-gasreaction, 10 se as to produce a streugly reducing, highlyheated, gaseousmedium in contact with a substantial portion of the inner surface ofsaid envelope and recovering the evolved gas. 1

In witness whereof, I have hereunto set 15 my hand at the city ofPittsburgh; county of Allegheny and State of Pennsylvania, this 1st dayof June, 1918.

CHARLES S, PALMER

